Thermosetting resin compositions are industrially useful as materials for, for example, mechanical components, electric and electronic devices, automobile components, construction/building and molding/forming, and further widely used also as materials for coatings and adhesives. In such thermosetting resin compositions, technologies of making the resin composition contain an inorganic substance in order to reduce a coefficient of expansion or to control an appearance have been widely studied, and for example, by matching a refractive index of the resin composition with that of the inorganic substance, the appearances of the resin composition and the cured formulation thereof are controlled and transparency is exhibited. Particularly in recent years, it is desired to increase the content of inorganic components in order to inhibit degradation of appearance during irradiation of light, but if the content of the inorganic components is increased, the transparency is impaired. Therefore, an attempt has been made to achieve compatibility between ensuring of the transparency and inhibition of the deterioration in appearance during irradiation of light by controlling a particle size distribution of the inorganic components in nanoorder.
With respect to a thermosetting resin composition containing an inorganic material, there is disclosed a metal oxide-epoxy resin composite in which metal oxide derived from metal alkoxide is finely dispersed in a size of 0.005 to 5 μm in a cured formulation of epoxy resin (for example, referring to Japanese Kokai Publication Hei-08-100107 (p. 2)). As a method for producing this composite, there is described a method for synthesizing the composite in situ by adding metal alkoxide and/or a partial hydrolysis condensation product thereof and water and/or an organic solvent to a solution formed by partially reacting an epoxy resin with an amine curing agent in advance.
And, with respect to a resin composition, there is disclosed an epoxy resin composition in which (a) an epoxy resin, (b) an epoxy resin curing agent, (c) a silane compound having one or more epoxy group or a group to perform an addition reaction with an epoxy group, and an alkoxy group bonded to two or more silicon atoms, and (d) a silane compound polycondensation catalyst are blended as essentially component (for example, referring to Japanese Kokai Publication Hei-10-298405 (p. 2)).
In such a resin composition, since inorganic matter exists as a particle precursor in preparing the resin composition, and it is necessary to allow a reaction of the particle precursor to proceed in molding/forming, the inorganic matter does not necessarily exist as a particle in a shaped article and it can form an interpenetrating polymer network with an organic component. There are occasions when a by-product is produced in molding/forming in some cases. Thus, in order to exploit the full potential of a thermal property or a mechanical property, it was necessary to control molding/forming conditions strictly and there was a room for improvement.
And, with respect to a resin composition, there is disclosed a thermosetting resin composition, which contains an epoxy resin (a), a reactant (b) of an organic silicon compound having a functional group capable of reacting directly or through medium of a curing agent with an epoxy group and an alkoxy group, tetraalkoxysilane and water, and a curing agent (c) (for example, referring to Japanese Kokai Publication 2001-288244 (p. 2-p. 4)). In these resin compositions, it is described to use a compound containing tin as a catalyst. Furthermore, with respect to a method for producing an epoxy resin composition, there is disclosed a method comprising adding alkoxysilane and water of pH 3 to 6 to an epoxy resin dissolved in an organic solvent, hydrolyzing an alkoxy group of alkoxysilane to a silanol group in presence of an acid catalyst and then removing the solvent, and filling particles obtained by subsequent heat treatment (for example, referring to Japanese Kokai Publication Hei-8-199045 (p. 2)).
Since these tin catalyst and acid catalyst will remain as impurities in the composition after preparing a resin composition, electric properties may be deteriorated when a shaped article absorbs moisture, and there was a room for improvement.
And, there is disclosed a solder resist composition containing alkoxy group-containing silane modified phenol, an epoxy resin and a solvent (for example, referring to Japanese Kokai Publication 2002-40663. However, when this composition is cured, a silane portion have to be condensated in curing the composition or prior to curing and methanol produced in this condensation have to be removed, therefore if the composition is used as a molding/forming material with thickness, foaming occurs and molding defect may arise. Accordingly, since the composition can be used only in film/thin layer form, there was a room for contrivance to be suitable for more uses.
And, there is disclosed a technique of mixing nano-silica dispersed in an epoxy resin and a phenol resin (for example, referring to Akio Takahashi, 5. et al. “Heat Resistant Epoxy-Silicon Hybrid Materials for Printed Wiring Boards”, ELECTRONIC CIRCUITS WORLD CONVENTION 9), paper No. JPCA04). In this documents, there is described a composition in which the content of a silica contained in an epoxy resin is 13.4% by weight, but it is estimated that in the whole cured formulation, this content of silica becomes a half of 13.4%. And, since as shown in Table 3, the coefficient of thermal expansion of the cured formulation is 43 at 50 to 100° C. and 162 at 200 to 250° C., the ratio of the coefficient of thermal expansion at 200 to 250° C. to the coefficient of thermal expansion at 50 to 100° C. is about 4. Therefore, in this technique, there was a room for contrivance to obtain a resin composition which can form a cured formulation having further excellent insulating property and thermal shock resistance and exhibiting a more excellent appearance.
On the other hand, when a cured formulation is obtained by using a polyhydric phenol as a phenol resin, the cured formulation has excellent properties, such as mechanical property and heat resistance. Therefore, the polyhydric phenol is used, for example, as an epoxy resin obtained by subjecting the polyhydric phenol to a glycidyl etherification, curing agent for an epoxy resin as well as a material for shape or a raw material for adhesive, coating material or the like, and the polyhydric phenol is very useful material. Among others, widely known is uses effectively utilizing an excellent electrical insulating property of the polyhydric phenol, such as a complex material of the printed circuit board and the like, a material for encapsulating semiconductor, a material for shape or adhesive and the like in electronic materials, such as an adhesive for IC package.
When the polyhydric phenol is used for electronic materials, the polyhydric phenol excellent in flame retardancy is particularly needed. As the polyhydric phenol having excellent flame retardant, for example, a bromine-containing epoxy resin and the like has been conventionally used. Recently, technologies for giving the flame retardancy without using halogen compounds have been developed. For example, an epoxy resin having excellent flame retardant, even though it is free from halogen, is obtained by adding nitrogen-containing phenol resin as a curing agent and further containing phosphate esters, or red phosphate as a flame retardant (referring to, for example, Japanese Kokai Publication Hei 08-253557, Japanese Patent No. 2975349, and Japanese Kokai Publication Hei 09-207271). However, there was a room for contrivance to obtain a flame retardant resin composition and a cured body thereof having no halogen and phosphate and having the flame retardancy, excellent properties of cured formulation, such as mechanical property and moisture resistance in various field.
The present inventors have studied on obtaining a hybrid and nano-composite resin by using silica, as a new flame retardant technology, in which neither halogen nor phosphate is used, and have found that a silica microfine particle having a specific structure may exhibit more excellent flame retardancy-providing performance than silica synthesized by the conventional methods (for example, referring to Japanese Kokai Publication 2003-344328). And the present inventors have succeeded in hybridizing a hydrolysis condensate of alkoxide and/or metal carboxylate as well as the silica obtained by the method, by mixing the hydrolysis condensation product to a polyhydricphenol bonding to each other with an organic skeleton having two or more carbon atoms therebetween, and have found that when the hybrid resin is used for a curing agent for epoxy resins, practically useful flame retardancy may be ensured without further addition of a flame retardant (that is, free from halogen and phosphate), and the present inventors have applied regarding these techniques (Japanese Patent No. 2002-151271).
Adding silica and the like to a resin composition as a filling agent is being examined in order not to give a flame retardancy but to improve various physical properties of a shaped body (cured body). For example, disclosed is a technology, in which strength, elasticity, and extension are improved by dispersing microparticles of a metal oxide (an average diameter is 0.01 to 5 μm), which is a hydrolysis polycondensation product of alkoxide, into a thermosetting resin without exhibiting macro phase separation (for example, referring to Japanese Kokai Publication Hei 08-259782). And disclosed is a thermosetting resin composition obtained by finely dispersing a silica and organopolysiloxane (0.005 μm to 0.01 μm), in which physical properties, such as shock resistance, heat resistance, flexural strength, and elasticity are improved (for example, referring to Japanese Kokai Publication Hei 09-208839). Furthermore, disclosed is a technique in which spherical amorphous silica microparticles having an average spherical diameter of 8 to 65 nm produced by a DC arc plasma process is preferably used as a silica filler for epoxy resin sealing material (For example, Japanese Kokai Publication 2000-319633).